Bryan Cranston's character Walter White has developed into a criminal mastermind as the series progressed. Photo / Supplied

Bryan Cranston is up for his fourth Emmy Monday for playing Breaking Bad's Walter White - once a mild-mannered chemistry teacher, now a drug kingpin who has seemingly crossed the line from conflicted anti-hero to outright villain.

As the show's fourth season heads to its climax, White now seems driven by greed and ego to the point where he's unwilling to walk away from his criminal empire, even though he could easily and safely return to his old life. But as series creator Vince Gilligan has pointed out, that stopped being an option for Walter some time ago.

From day one, Breaking Bad has been described as "Mr Chips becomes Scarface" - how bad can Walter White get before audiences are completely turned off by him?

I torture myself with that; I lost sleep for several seasons. I worry about where we are going. If the character isn't likeable, who is going to watch him? You have to set the show off on the right foot.

You have to show why Walter White was making these bad decisions. This show was always a kind of experiment - to show a transformation of the main character and have a good guy by force of will transform himself into the bad guy. If you embrace that mandate that we gave ourselves with courage then you have to say to yourself that this guy will get worse with every episode.

Every audience member has a threshold of disgust but with every episode someone else watching the same episode will say, "Ugh, I can't watch this any more." In the early seasons I was worried about shedding viewers but I came to realise even if this character becomes unlikeable, we will be in pretty good shape as long as he remains interesting. So far, so good. Even the viewers for the most part seem to be very engaged and enthusiastic towards the show - even the ones who don't sympathise with the character. Walter has an amazing instinct for survival and manages to get himself out of very tight scrapes and they are intrigued about what comes next.

We've discovered more and more about Walter as the series has progressed. Have you discovered just as much along the way?

Walter White is a damaged individual, and I didn't realise this in the beginning. You would think I would know who he was from the get-go. When a show runs for many seasons, it's a living, breathing thing and you learn more about the character you are writing about. What I have learnt now about Walt is he is a man of great pride and a man of very low self-esteem. Because of that, the self-aggrandisement that he feels about being a kingpin is a yardstick he uses to measure himself up against. Up until the day he started doing this he didn't think he had any power.

At the same time, there's this undercurrent of anger and frustration because no one is recognising his criminal genius.

There is a strange tension there, a strange duality. On the one hand he wants to stay out of trouble but on the other hand if you are Jesse James and the world doesn't know it ... As much as he doesn't want to go to prison, he does want the world to know his prowess. That's the tension as the series progresses.

Do you think Walter will ever try his own product?

You'd be surprised as to how often that comes up. We have floated that idea about half a dozen times. Never say never, but it seems Walt is hooked on power and process and the process of cooking meth is an addiction to him. The role of kingpin and watching the money stack up intrigues him and appeals to him. He feels like a man who would not risk any of those greater highs by becoming sloppy. If he was on meth he would be awake more to cook more meth but the quality wouldn't be as good. And I feel that it would be anathema to him.

Do you feel we're in a golden age of television?

I think we have had several [of those] and I think we are in the midst of another. This is certainly the greatest freedom I have ever had and the greatest, most pleasurable working situation I have ever had. I have written movie scripts that have been made and they haven't been great experiences. In television, the writer is the boss and, man, I love that. Who wouldn't love that?

TV ProfileWhat:Breaking Bad, Emmy nominated drama which has Bryan Cranston up for his fourth best drama actor Emmy.